Fuse cartridges

ABSTRACT

In an electrical fuse cartridge having a hollow insulating body enclosing the fusible element or elements and carrying the terminal heads of the cartridge, the said body is formed of a tubular mass of an insulating material in which a tube is embedded for circulation of a cooling fluid. The tube is preferably of non-metallic nature and it is coiled helically about the axis of the body. In a preferred embodiment the tubular mass is obtained by winding on a mandrel glass threads or ribbons impregnated with a uncured synthetic resin so as to form an inner layer on which the cooling tube may be coiled, then an intermediate layer which fills the helical space which separates the successive turns of the coiled tube, and an outer layer covering the intermediate layer and the tube, the unit thus obtained being thereafter treated to cure the resin in the three layers and to thus obtain a rigid one-piece body with the cooling tube embedded therein.

United States Patent 1191 Fontaine Feb. 19, 1974 FUSE CARTRIDGES PrimaryExaminer-Gilheany Bernard A.

Assistant ExaminerF. E. Belli [75] Inventor' jg g Fontaine EculnyAttorney, Agent, or Firm-Alexander & Dowel] [73] Assignee: SocieteLucien Ferraz & Cie, [57] ABSTRACT Lyon/Rhone France In an electricalfuse cartridge having a hollow insulat- [22] Filed: July 17, 1972 ingbody enclosing the fusible element or elements I and carrying theterminal heads of the cartridge, the 1 Appl' 272l60 said body is formedof a tubular mass of an insulating material in which a tube is embeddedfor circulation I52] U.S. Cl. 337/166, 174/15 R, 337/185 of a coolingfluid. The tube is preferably of non- [51 I Int. Cl. H0lh 85/04 metallicnature and it is coiled helically about the axis [5 F eld Of 5, 163; l6of the body. In a preferred embodiment the tubular 174/ 15 R mass isobtained by winding on a mandrel glass threads or ribbons impregnatedwith a uncured syn- [5'6] References C ted thetic resin so as to form aninner layer on which the UNITED STATES PATENTS cooling tube may becoiled, then an intermediate layer 3,453,579 7 1969 Cinquin 337/166 uxwhich fills the helical Space which separates the 3,678,431 7/1972Franklin 337/185 cessive turns the coiled tube and an outer layer3,713,065 1 1973 Brichant.. 337 166 covering the intermediate layer andthe tube, the unit 3,715,698 2/1973 Blewitt 337/185 thus obtained beingthereafter treated to cure the 3,693,71 1 9/1972 Zygiel 165/164 resin inthe three layers and to thus obtain a rigid one- 3,586,9l7 6/1971 Oatesl74/l5 R piece body with thg COQIiEg tube embedded therein 2 Claims, 3Drawing Figures FUSE CARTRIDGES The present invention relates to fusecartridges which are used as protecting means against excessive currentsand shortcircuits.

' These'cartridges comprise a generally tubular insulating body whoseends are closed by metallic heads which carry the contact members of thecartridge, these heads being connected with each other within thecartridge body by fusible elements (wires or strips) embedded in a massof arc-quenching material (generally quartz sand).

Under the action of an excessive current or shortcircuit the fusibleelements melt or volatilize and the are which appears between the headsis rapidly quenched by the sand or like material. But this are creates asudden gaseous overpressure or pressure wave which is applied to theinsulating body. The latter should therefore have a relatively highmechanical strength to withstand this bursting action. 'j The cartridgebody should also evacuate the heat generated by the electric current inthe fusible elements. Since the latter should melt under the action ofan excessive current, it is unavoidable that under normal conditionsthey cause a slight voltage drop which is transformed into heat. Thisheat is'in part transferred to the arc-quenching material and therefromto the cartridge body. Owing to the thermic conductivityof the fusibleelements a noticeable portion of the heat thus generated is alsotransferred to the said body through the metallic heads of thecartridge.

lt has been proposed to cool the body of a fuse cartridge by means of anappropriate liquid (oil, demineralized water, etc...). For this purposethe cartridge body may be realized under flat form, liquid cooledmetallic plates being applied against its sides. But of course such anarrangement is only effective for the outer surface ofthe body and sincedue to the required mechanical strength the latter should be relativelythick while being madeof an insulating material of low thermalconductivity the temperature gradient across the body wall is relativelyimportant and limits the cooling possibilities. It has further beensuggested to cool a fuse cartridge through its heads, but this is onlyeffective in the case of cartridges of'short length.

It is an object of the present invention to avoid the above-mentionedlimitations and to provide a liquid cooled fuse cartridge having aninsulating body of high mechanical strength with a high heat dissipatingcapacity.

In accordance with the present invention a hollow body for a liquidcooled electrical fuse cartridge comprises a cooling tube embedded in atubular mass of an insulating material.

In 'a preferredembodiment the cooling tube, which is conveniently madeof a plastic or synthetic material, is coiled helically co-axially tothe cartridge body, the tubular mass in which it is embedded beingformed of a hardened synthetic resin re-inforced by a fibrous materialwith fibres extending substantially circularly about the aforesaid axis.The fibrous material used comprises preferably glass fibres.

The invention further concerns a process for the manufacture ofacartridge body by winding on a mandrel three layers of a textilematerial with longitudinallyextending fibres, impregnated with asynthetic resin in the non-hardened state, namely an inner layer onwhich the cooling tube is coiled, an intermediate layer which 7 fillsthe spaces between the successive turns of the helically coiled coolingtube, and an outer layer which covers the said tube, the mass thusobtained being thereafter treated so as to harden the synthetic resinand to obtain a one-piece rigid hollow body in which the cooling tubeisembedded.

In the annexed drawings:

FIG. 1 is a side view with fragmental section of a fuse cartridgecomprising an insulating body according to the invention.

FIG. 2 is a transverse section thereof.

FIG. 3 is a fragmental longitudinal section of a cartridge bodyaccording to the invention obtained by winding appropriately impregnatedglass threads or ribbons.

. The cartridge illustrated in FIGS. 1 and 2 comprises a tubularinsulating body 1 the ends of which are closed by two metallic heads 2,each being in one with a contact blade 3. These heads 2 are secured tothe body 1 by any appropriate means not shown. They may be formed forthis purpose with an inner portion of reduced diameter which fits intothe corresponding end of body 1. Heads 2 are electrically connected witheach other by means of a fusible strip 4 which is pleated in accordionfashion within body 1, this strip being embedded in a mass 5 of anappropriate arc-quenching material, such as for instance quartz sand.

In the embodiment illustrated the cartridge body 1 has a more or lesselliptical transvers profile and strip 4 is so arranged that the ends ofits successive folds may come into contact with the inner surface of thesaid body. Such an arrangement reduces to a minimum the averagethickness of the material 5 which separates the strip from the body walland enhances heat'transfer between the strip and the said body.

As above indicated the cartridge body 1 includes a coiled tube 6 whichis embedded in the thickness of the wall thereof, this tube havingoutwardly extending ends 7 and 8 through which it may be connected withan appropriate system of cooling liquid. Tube 6 may be made of metal,more particularly in the case of low voltage circuits, but it seemspreferable to use a tube made of an appropriate plastic or syntheticmaterial in order to avoid the presence of an electrically conductivemember which may cause superficial electrical leaks or facilitate theformation of an outer are between the cartridge heads under the actionof the voltage surge which generally appears when the fusible elementmelts under a heavy current.

The cartridge body may be made of any insulating 'material capable ofbeing moulded or otherwise disposed around the coiled tube. It may moreparticularly be realized in an appropriate plastic or synthetic materialby injection moulding within a mould provided with means for retainingthe coiled tube at the proper position in the moulding cavity. In such acase, if the tube is itself made of a plastic or synthetic material, thelatter should of course be of such a'nature as to withstand theinjection temperature without being damaged, which may be difficult insome cases. Furthermore a hollow body made of an injected material doesnot generally possess a very high mechanical strength against bursting.ltseems therefore preferable to realize body 1 in the following manner:

There is first prepared a mandrel having the dimensions desired for theinside of the said body. Threads or ribbons of an appropriate materialunder fibrous form, preferably glass, are then would on this mandrelwhile being impregnated with a thermosettable synthetic resin in theunhardened state until there is obtained a layer having a thickness a(FIG. 3) equal to the distance desired between the coiled cooling tubeand the inner surface of the cartridge body. The cooling tube 6 is thenwound on this first layer. If required the tube may be heated at such atemperature that it may be sufficiently deformable for the windingoperation. Also care must be taken that it should not flatten, as thisis well known in the art. The coiled tube thus realized is thenmaintained on the mandrel and appropriately impregnated strips of glassthreads or ribbons are wound in the helical spaces which separate thesuccessive turns of the tube until the said spaces are wholly filled,which corresponds to the thickness b in FIG. 3. Finally an outer layerof impregnated glass threads or ribbons is wound on the smoothcylindrical surface thus realized so as to form an outer layer havingthe thickness c which is desired for the insulating material coveringthe coiled tube.

After treatment of the resin and removal of the mandrel, there is thusobtained a one-piece tubular body of considerable mechanical strengthagainst inner pressure waves and in which the coiled cooling tube iswholly embedded.

Whatever may be the method used for the manufacture of the cartridgebod'y according to the invention, this body may be cooled in a regionclose to its inner surface, i. e., with a much lower temperaturegradient than by means of the known outer cooling plates. If the coolingtube is made of a plastic or synthetic material,

the cartridge body comprises no electrically conduct- .ing part whichcould lead to the formation of an arc when the fusible elementvolatilizes under the action of an excessive current or of ashort-circuit.

It is to be noted that the cooling tube could be coiled in zig-zagformationincluding straight portions parallel to the cartridge axis andconnected with each other in V series by semi-circular portions. In somecases the cooling system could comprise a number of longitudinal tubesconnected in parallel between two headers. Of course with non-helicalformations the spaces between the coils or sections'can no more befilled by winding threads or ribbons of a fibrous material such asglass, and it is therefore necessary to provide a moulding operation atleast'for the thickness b of FIG. 3.

I claim:

1. A process for the manufacture ofa cartridge body,

comprising the following steps:

a. winding on a mandrel a first textile material with longitudinallyextending fibers to form an inner layer on said mandrel, said firstmaterial being impregnated with an uncured synthetic resin;

b. winding helically a cooling tube on said inner layer with thesuccessive turns being separated from each other by a helicalintermediate space;

c. winding helically on said inner layer and in said helicalintermediate space a second textile material with longitudinallyextending fibers to form a helical intermediate layer which completelyfills said space and realizes on said mandrel a substantially smoothperipheral surface, said second textile material being impregnated withan uncured synthetic resin;

d. winding on said smooth surface a third textile material withlongitudinally extending fibers, to form an outer layer which coverssaid intermediatelayer and said tube, said third textile material beingimpregnated with an uncured synthetic resin;

e. treating the tubular mass thus obtained on said mandrel to cure thesynthetic resin in said'inner, intermediate and outer layers and to thusform a one-piece rigid hollow body.

2. In a process as claimed in claim 1, one at least of said first,second and third textile materials comprising glass fibers.

1. A process for the manufacture of a cartridge body, comprising thefollowing steps: a. winding on a mandrel a first textile material withlongitudinally extending fibers to form an inner layer on said mandrel,said first material being impregnated with an uncured synthetic resin;b. winding helically a cooling tube on said inner layer with thesuccessive turns being separated from each other by a helicalintermediate space; c. winding helically on said inner layer and in saidhelical intermediate space a second textile material with longitudinallyextending fibers to form a helical intermediate layer which completelyfills said space and realizes on said mandrel a substantially smoothperipheral surface, said second textile material being impregnated withan uncured synthetic resin; d. winding on said smooth surface a thirdtextile material with longitudinally extending fibers, to form an outerlayer which covers said intermediate layer and said tube, said thirdtextile material being impregnated with an uncured synthetic resin; e.treating the tubular mass thus obtained on said mandrel to cure thesynthetic resin in said inner, intermediate and Outer layers and to thusform a one-piece rigid hollow body.
 2. In a process as claimed in claim1, one at least of said first, second and third textile materialscomprising glass fibers.